Feedwater heater

ABSTRACT

A feedwater heater for use in a power plant system in which steam from another unit in the system is introduced into the shell of the heater and the latter discharges condensate to another unit in the system. Feedwater to be heated is circulated through tubes in the shell in heat exchange relation to the steam whereby a portion of the steam is condensed. Another portion of the steam is directed to an area of the shell where it warms the condensate to a degree that maintains the condensate at or near its saturation temperature. An additional inlet is provided in the shell for receiving condensate from another unit of the system along with means for breaking up the flow of the latter condensate to promote deaeration as a portion of the condensate flashes into vapor. The vapor produced as a result of the flashing is directed in the same flow path as the above-mentioned steam, and vent means are provided for permitting the removal of the non-condensibles and associated water vapor from the shell.

United States Patent [191 Brigida et a1. 7

Mar. 5, 1974 1 FEEDWATER HEATER [75] Inventors: Carlo J. Brigida, Long Island, N.Y.;

Meyer Wexler, Rahway; Philip S. Woodford, Convent Station, both of NJ.

[73] Assignee: Foster Wheeler Corporation,

Livingston, NJ. 22 Filed: June 12, 1972 [21] Appl. No.: 261,774

[52] US. Cl 165/112, 60/95 R, 122/441, 165/1 14 [51] Int. Cl F28b l/02 [58]' Field of Search 165/112, 114; 60/95 R; Y 122/441 [56] References Cited UNITED STATES PATENTS 2,354,071 7/1944 Smith 165/114 2,939,685 6/1960 Worn et a1... 165/114 2,956,784 10/1960 Parkinson.... .165/114 X 2,995,341 8/1961 Danesi...- 165/110 3,061,273 10/1962 Dean, Jr. et al. 165/114 3,698,476 10/1972 Wyzalek I65/l l2 FOREIGN PATENTS OR APPLICATIONS 264,141 4/1929 ltalyu. 165/114 OOQOOOOO Primary Examiner-Albert W. Davis, Jr. Attorney, Agent, or Firm-Marvin A. Naigur; John E. Wilson ABSTRACT A feedwater heater for use in a power plant system in which steam from another unit in the system is introduced into the shell of the heater and the latter discharges condensate to another unit in the system. Feedwater to be heated is circulated through tubes in the shell in heat exchange relation to the steam whereby a portion of the steam is condensed. Another portion of the steam is directed to an area of the shell where it warms the condensate to a degree that maintains the condensate at or near its saturation temperature. An additional inlet is provided in the shell for receiving condensate from another unit of the system along with means for breaking up the flow of the latter condensate to promote deaeration as a portion of the condensate flashes into vapor. The vapor produced as a result of the flashing is directed in the same flow path as the above-mentioned steam, and vent means are provided for permitting the removal of the noncondensibles and associated water vapor from the shell.

8 Claims, 5 Drawing Figures PATENTEUHAR 5:974

SHEEI 1 0F 2 w I O, u 0

PATENTED 4 3.795.213

SHEEI 2 UF 2' OOOOOOOO v ter heater of the line 4-4 of FIG. 3;

1. FEEDWATER HEATER BACKGROUND OF THE INVENTION This invention relates to a feedwater heater, and more particularly to such a heater for effecting a heat exchange between steam and feedwater, while removing non-condensibles from the steam and condensate.

Heaters are often employed in power plants to provide a heat exchange function between the steam used in another unit of the power plant and feedwater before it passes into a boiler or the like. In general, feedwater heaters are provided to heat the feedwater prior to entering the boiler. Feedwater heaters which heretofore have been used, afford removal of non-condensibles that are present in the shell. The instant invention allows for the removal of additional non-condensibles that would normally remain dissolved in the condensate that is passed out of the feedwater heater.

SUMMARY OF THE INVENTION shell, a plurality of tubes for circulating water throughsaid shell, means for directing steam through said shell and over said tubes to heat said water, a portion of said steam separating into condensate and noncondensibles, and means for heating said condensate to a degree that maintains it at or near its saturation temperature. An additional inlet is also provided forreceiving a condensate from another unit of said system, along with means for breaking up the flow of said condensate to promote removal of non-condensibles as a portion of the condensate flashes into vapor. Vent means are provided to remove the non-condensibles and associated water vapor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of the feedwapresent invention with the components therein being shown in perspective for the convenience of presentation;

FIGS. 2 and 3 are enlarged sectional views taken on I the lines 2-2 and 33, respectively, of FIG. 1;

FIG. 4 is an enlarged sectional view taken along the and FIG. 5 is an enlarged sectional view taken along the line 55 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring specifically to.the drawings, the reference numeral refers in general to the feedwater heater of the present invention which comprises an outer elongated shell 12 having one closed end and the other end registering with a header 14. The header 14 is of a con ventional design and includes an inlet 16 and an outlet 18 for feedwater. A plurality of U-shaped tubes 20 are supported within the shell 12 and are represented schevide for uniform distribution matically by lines since the scale does not permit proper elevational or sectional views. The lower leg of each tube, as viewed in FIG. I, registers with the inlet 16 via a chamber (not shown) formed in the header 14, and the upper leg of each tube 20 registers with the outlet 18 via an additional chamber formed in the header 14. The tubes 20 are supported in the shell 12 by means of a plurality of vertical partitions 22 which are shown in a perspective view in FIG. I for the convenience of presentation, it being understood that they normally extend at right angles to the plane of the drawing. An end plate 23 is positioned beyond the tubes 20 to form a flash chamber 24 at the end of the shell 12.

A steam inlet 25 is provided in the upper wall of the shell 12 with a deflector plate 26 being disposed on one of the central partitions 22 to deflect the steam entering the shell in a generally horizontal direction. A pair of vent pipes 28 and 30 are disposed in the shell 12 and each is connected to the end partition 22. The vent pipes 28 and 30 have a plurality of perforations formed therethrough, with the perforations being shown in general by the reference numeral 30a in connection with the vent pipe 30 in FIG. 1, it being understood that the vent pipe 28 is similarly perforated. It is also under stood that the connections between the ventpipes 28 and 30 are such that the vent pipes can be connected to another unit of the same system in which the heater 10 is connected. Preferably, this latter unit is at a'relatively low pressure so that the vent pipes 28 and 30 establish the lowest pressure point within the shell 12, for

reasons that will be apparent from the following. An

outlet 32 is provided in the bottom portion of the shell 12 for discharging condensate from the shell 12.

The tubes 20 are formed into two tube bundles 20a and 20b which are separated by a vertical channel 34, as shown in FIG. 2. Each bundle, in turn, is separated into an upper and lower portion by a horizontal channel 36 due to the fact that the tubes 20 are U-shaped, with the width of the channel 36 corresponding to the spacing between the two legs of the innermost tubes. An additional horizontal space 38 is provided in the lower portion of each tube bundle 20a and 20b to mo of steam into each of the tube bundles 20a and20b, as will hereafter be explained in detail.

A pair of baffles 40 and 42, shown in section in FIG. 2 and partially cut away in FIG. 1, are provided in the lower section of the shell 12. Each of the baffles 40 and 42 is formed by two legs which meet at an angle, with the apex of the angles extending over the vent pipes 28 and 30, respectively. One leg of each baffle 40 and 42 extends through the tube bundles 20a and 20b, respectively, and the other leg extends around the outer periphery of the tube bundles 20a and 20b, respectively, as viewed in FIG. 2. The purpose of the baffles is to direct steam from the inlet 25 in a particular direction relative to the tubes 20 as will be ex- 7 plained in-detail later. A pair of drain trays 43 are lodensate will largely consist of water having noncondensibles dissolved therein.

As better shown in FIGS. 3 and 4, the inlet pipes 44 and 46 are perforated to permit the condensate discharging therefrom to spread out in a radial direction. A stainless steel liner 48 is disposed in the shell 12 and is integrally formed with a lip portion 50 adapted to prevent direct impingement of the flow from inlets 44 and 46 onto the tube bundles 20. Thus, impingement on tubes is prevented by the barrier in flash chamber 24 created by the lip portion SOand end plate 23. It should be noted that the space between the lip portion 50 and the end-plate 23 is sized for the flow of flashed steam out of flash chamber 24. It should also be noted that in some designs, the liner 48 covers the entire back end of the shell 12. The liner 48 also has a perforated, horizontally extending, lip plate 52 which also breaks up the discharge from the pipes 44 and 46, before the discharging condensate impinges on a plurality of flat bars 54 which are attached to the back of the shell 12 and extend immediately below the lip plate 52 for further breaking up the discharging condensate.

The pressure in the shell 12 is lower than that of the pressure of the source of the condensate entering through the drain lines 44 and 46, so that due to the pressure differential the latter condensate will flash, with the end plate 23, liner 48, lip portion 50, lip plate 52, and flat bars 54 breaking up the flow to allow for a greater amount of dissolved non-condensibles to be removed as the flashing occurs. A pair of shields 56 and 58 having an open bottom end portion are supported by the left end partition 22 and direct the vapor resulting from the above-mentioned flashing, along with the non-condensible vapors. into the vent pipes 28 and 30.

In operation, feedwater is admitted into the inlet 16 of the header 14 whereby it is heated as it circulates through each of the U-shaped tubes 20. The heated feedwater exits from the outlet 18 and is fed to another stage of the system, such as a boiler. Steam from still another stage of the system, suchas from a steam turbine, and consisting largely of water vapor and noncondensibles, enters the shell 12 through the inlet 25, is deflected in a generally horizontal direction by the deflector 26, and passes into the various sections of the heater defined by the partitions 22.

The steam takes the flow pattern within each individual section as shown by the arrows in FIG. 2, i.e., through the upper portions of the tube. bundles 20a and 20b and downwardly through the lower portions thereof. In this manner, a portion of the steam will pass over the tubes 20 whereby a portion thereof will condense as a result of giving up heat to the feedwater passing over the tubes, with the non-condensibles being carried over to the baffled portion of the tube bundles 20a and 20b. The steam not condensing at the upper 7 leg portions of the tubes 20 will be directed by the baffles 40 and 42 over the, lower leg portions of the tubes in the manner shown by the arrows in FlG.'2,,whereby a portion of it will condense in a similar manner. The steam not condensed at either the upper or lower leg portions of the tubes, along with the non-condensibles present in the vicinity of the tubes is directed by the baffles 40 and 42 into the low pressure vent pipes 28 and 30 and thus discharged from the unit, with the spaces 38 formed in the tube bundles insuring a more uniform distribution of the steam to the tube bundles 20a and 20!). Still another portion of the steam from the inlet 24 will pass directly through the vertical channel 34 without encountering any of the tubes 20 and will flow to the lower portion of the shell 12. This steam will maintain the condensate formed on the outer surface of the tubes 20 as a result of the above condensation of steam, at a relatively elevated temperature in order to maintain it at or near its saturation temperature, and thus prevent the condensate from being sub-cooled. This prevents this condensate from absorbing any of the non-condensibles originally present in the steam or otherwise present in the shell, and thus permits the latter vapors to be drawn into the vent pipes 28 and 30.

Drains, in the form of condensate containing noncondensibles, pass into the flash chamber 24 of the shell 12 through the drain lines 44 and 46, and are broken up by the end plate 23, liner 48, lip portion 50, lip plate 52, and flat bars 54, thereby allowing for a greater amount of non-condensibles to' be removed as flashing occurs. The resultant vapor, including the noncondensibles, passes either directly into the ends of the vent pipes 28 and 30 for discharge, or into the other section of the heater over the top or bottom end portions of the partitions 22, whereby it joins the steam entering through the inlet 24 to take the flow pattern, and thus be treated, as discussed above.

It should be noted that most of the steam (either entering through inlet 25 and the flashed steam from the flow entering through connections 44 and 46) will be condensed and will join the remaining condensate from drain lines 44 and 46 in the bottom portion of the shell 12 and will exit through outlet 32 to another unit in the system, such as a heater or condenser.

Thus, a highly efficient heat transfer will be effected since the condensate is maintained at or near its saturation temperature and will thus absorb very little of the non-condensibles present within the shell 12. Also, these non-condensibles are effectively discharged from the vent pipes 28 and 30 and out through the header 14.

Of course, several variations may be made of the foregoing without departing from the scope of the invention. For example, a perforated steam pipe 60 may be disposed in the bottom portion of the shell 12 shown in FIG. 1 to provide a direct source of steam to this area and to function to heat the condensate draining off tubes 20 in the same manner as the steam passing through the vertical channel 34. While the steam pipe 60 is shown in FIG. 2 as being located above the water line, it should be understood that the steam pipe 60 can also be located below the water line. Also, several inlets 25 may be provided along the longitudinal length of the shell instead of the single inlet shown. Further, the shell may be adapted for vertical operation in which case the structure would be altered slightly for routing the vapor and condensate in the above fashion.

It is understood that other variations may be made in the foregoing without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

l. A feedwater heater capable of receiving steam and drain flows containing non-condensibles from at least one external source, comprising a shell having an inlet for receiving steam, an inlet for receiving drain flows, and an outlet for discharging condensate; a plurality of tubes for circulating water through said shell; means for directing said steam through said shell in a direct heat exchange relation to said water to condense a portion of said steam and heat said water; means for heating the condensed steam to a degree that maintains it at or near its saturation temperature; an end plate disposed in said shell and separating said tubes from the end of said shell to define a flash chamber; a baffle plate and a plurality of bars mounted in said flash chamber in the path of said drain-flows to break up said drain flows to promote the removal of said non-condensibles as flashing occurs; and vent means for conveying said noncondensibles out of said shell.

2. The heater of claim 1 wherein said baffle plate is in the form of a perforated lip integral with a liner disposed in said flash chamber.

3. The heater of claim 1 wherein said bars extend parallel to the longitudinal axis of said shell and extend across a portion of said flash chamber.

4. The heater of claim 1 wherein said baffle plate extends between said drain flows inlet and said bars.

5. The heater of claim 1 further comprising baffle means for directing non-condensibles from said steam and said drain flows and that portion of said steam that doesnt condense into said vent means.

6. The heater of claim 1 wherein said heating means comprises means for providing an external source of steam to said shell to maintain the condensate at satubetween said tubes to the bottom of said shell. 

1. A feedwater heater capable of receiving steam and drain flows containing non-condensibles from at least one external source, comprising a shell having an inlet for receiving steam, an inlet for receiving drain flows, and an outlet for discharging condensate; a plurality of tubes for circulating water through said shell; means for directing said steam through said shell in a direct heat exchange relation to said water to condense a portion of said steam and heat said water; means for heating the condensed steam to a degree that maintains it at or near its saturation temperature; an end plate disposed in said shell and separating said tubes from the end of said shell to define a flash chamber; a baffle plate and a plurality of bars mounted in said flash chamber in the path of said drain-flows to break up said drain flows to promote the removal of said non-condensibles as flaShing occurs; and vent means for conveying said noncondensibles out of said shell.
 2. The heater of claim 1 wherein said baffle plate is in the form of a perforated lip integral with a liner disposed in said flash chamber.
 3. The heater of claim 1 wherein said bars extend parallel to the longitudinal axis of said shell and extend across a portion of said flash chamber.
 4. The heater of claim 1 wherein said baffle plate extends between said drain flows inlet and said bars.
 5. The heater of claim 1 further comprising baffle means for directing non-condensibles from said steam and said drain flows and that portion of said steam that doesn''t condense into said vent means.
 6. The heater of claim 1 wherein said heating means comprises means for providing an external source of steam to said shell to maintain the condensate at saturation temperature.
 7. The heater of claim 1 wherein said heating means comprises means for directing steam around various sections of said tubes.
 8. The feedwater heater of claim 7 wherein said means for directing steam flow around various sections of said tubes comprises a plurality of partitions disposed in said shell, a portion of said tubes being spaced from another portion, whereby an uninterrupted flow of a portion of said steam is provided through spaces between said tubes to the bottom of said shell. 